Numerous clinical studies have related overall respiratory heat and/or water exchange to exercise-induced bronchoconstriction or post-exertional cough, in susceptible subjects. Although these studies have provided considerable insight into the mechanisms underlying these clinically important problems, their implications have been limited in part by an inadequate understanding of the presumed stimuli - respiratory heat and water loss. Previously, respiratory heat and water loss have been assessed only in a global fashion, reflecting overall exchanges occurring at all sites within the airways. The basic premise of this proposal is that a detailed knowledge of the sites and magnitudes of respiratory heat and water exchange would allow investigators to discern which qualities of the distributed respiratory thermal events during exercise or hyperpnea are important in precipitating bronchoconstriction and cough. It is the objective of this proposal to employ an invasive and a non-invasive technique, each of which will allow determination of local heat and water exchanges at many sites throughout canine airways. Using these two approaches, the studies proposed herein will examine the influence of breathing pattern, blood flow within the pulmonary and bronchial circulations, and bronchoconstriction on the distribution of respiratory heat and water exchanges. These data should prove useful in providing a better appreciation of the important factors controlling these processes, and should lead to a better understanding of the mechanisms responsible for exercise-induced airways response in humans.